1. Technical Field
This invention relates generally to color copiers and printers, and more particularly to automatic adjustment of parameters influencing the output image color balance, color fidelity, and tone reproduction.
2. Background Art
In electrostatographic image production, several factors inhibit perfect and constant color reproduction in terms of color balance, color fidelity, and tone reproduction. These factors include, among others, variation in the toning contrast in the different color development stations.
Prior art systems attempt to diminish the adverse effects of these factors using either manual or automatic set up systems, or a combination of both. In typical manual set up systems, a skilled operator examines the output image and the corresponding input and output density (D.sub.in -D.sub.out) curves for red, green, blue, and black. Based on experience with the equipment, the operator determines adjustments to process control parameters, such as initial voltage V.sub.0, exposure E.sub.0, and development bias V.sub.b. Several iterations of adjustment may be required to achieve acceptable color reproductions.
Automatic set up processes are known for adjusting one or more of the process control parameters affecting the output color and density. Such automatic adjustment is typically based on density measurements of toned test patches for each color separation. Whatever the set up procedure, good quality color reproductions can be made with a particular set up only so long as the toner development characteristics of each development station remains constant.
One factor which influences the development characteristics of a development station is the concentration of toner particles in the development mixture. Toner concentration monitors have been used for maintaining consistency in the toner concentration and/or for adjusting process control parameters based on the amount of toner particles in the mixture.
Other factors, such as mass, time, humidity, and charge ultimately affect the developed image. Therefore, commonly assigned, co-pending U.S. patent application Ser. No. 546,983 filed in the names of D. S. Rimai et al. on Jul. 2, 1990 now U.S. Pat. No. 5,006,897, discloses a toner development rate monitor for controlling process control parameters to give improved development performance.
A disadvantage to prior art systems is that they are adapted to control the process only for a particular development station and for the color separation associated with that particular development station. They are essentially feedback systems which endeavor to correct future images when a situation is detected in an earlier image production process.